Field
This invention relates generally to data communications, and more specifically, to a method and system to balance web server load based on global geographic location.
Background
Web sites are known to use many web servers to serve large numbers of web clients accessing the web sites. The web servers, or application delivery servers, deliver web applications such as web pages, videos, file transfers, photo transfers, office applications, email applications, enterprise web applications and many other consumer and enterprise applications using web technologies. In a typical deployment scenario, the web servers are behind a server load balancer (SLB). The SLB receives a web service request from a web client, selects a web server, and relays the web service request to the selected web server. The network architecture using a SLB and a plurality of web servers allows not only a web site to serve many web clients, but also provides fault resiliency to a web site in case one or more web servers fail, while the remaining web servers continue to provide web services. A web site may deploy a plurality of SLB's to provide fault tolerance to one or more SLB failures. However, as a web site grows in popularity, a single or a few SLB's with a plurality of web servers may not be sufficient. Large number of SLB's and a very large number of web servers are necessary to serve a large web site such as google.com or yahoo.com.
Moreover, the large number of web servers and SLB's are hosted in a plurality of data centers, so as to provide further fault tolerance in case of data center failure. The data centers are usually far apart, with at least tens or hundreds of miles apart. When a web client accesses the web site, the web service request is assigned to a web server in one of the data centers. The quality of the web service then depends on the chosen data center, where the service quality may depend on the distance between the data center and the web client, the load of the web servers in the data center, the network capacity of the web servers in the data center to the web client, and other network or computing factors between the data center and the web client. Thus the location information of the web client becomes an important factor in selecting a data center, and in selecting a web server of the data center to serve the web service request from the web client.
It is common to use a Domain Name System (DNS) to deploy a plurality of web servers for a web service based on a Uniform Resource Locator (URL). In one embodiment, a web client sends an inquiry to a DNS server with a domain name, which is a part of the URL. A DNS server responds with a plurality of records, each of which refers to a web server. In various methods, the web client uses the plurality of records referencing the plurality of web servers to determine a particular web server, the web client selects a web server using a round robin scheme on the plurality of web servers, the web client selects a web server used in a previous web session on the same web service, or the web client selects a web server different from a previous web session on the same web service where the previous web session encountered an error.
In one method, a local DNS server assists the web client in selecting a web server. The local DNS server receives information for a plurality of web servers from a global DNS server. In one embodiment, the local DNS server selects a web server from the plurality of web servers. For example, the local DNS server selects a web server using a round robin scheme. In one method, the local DNS server selects the first web server from the plurality of web servers.
However, as mentioned above, there is no existing method to select a web server based on location information or to balance web server load based on location information, so as to provide a better web service, and to provide fault tolerance upon data center failure.
Therefore, there is a need for a system and method to balance web server load based on location information of a web client.